Determination of area-averaged water vapour fluxes with large aperture and radio wave scintillometers over a heterogeneous surface - Flevoland field experiment

A large aperture scintillometer (LAS) and radio wave scintillometer (RWS) were installed over a heterogeneous area to test the applicability of the scintillation method. The heterogeneity in the area, which consisted of many plots, was mainly caused by differences in thermal properties of the crops; the variations in the aerodynamic roughness length were small. The water vapour fluxes derived from the combined LAS-RWS system, also known as the two-wavelength method, agreed fairly well with the aggregated water vapour fluxes derived from in-situ eddy covariance measurements. The water vapour fluxes derived from a stand-alone LAS are also presented. It was found that a single LAS and an estimate of the area averaged available energy (using a simple parameterisation scheme) can provide also reasonable area-averaged water vapour fluxes.